Fluid level sensors that use capacitors for the primary sensing elements are well known. However, prior devices have numerous drawbacks which result in either excessive cost, decreased accuracy or poor reliability and maintainability over extended periods of use. For example, ring plate capacitor devices are difficult, and hence costly, to manufacture. Detectors that use separate electronic circuits for each capacitor or group of capacitors require time-consuming and labor-intensive calibrations. RF circuits require extensive and precision components that introduce a much greater likelihood that one of those circuits will drift with age. Also, multi-circuit detectors must be reconfigured for each tank or container design.
The need, therefore, has long existed for an accurate yet inexpensive apparatus for detecting the level or quantity of fluid in a container.